New Light Shed on Landscape Groundcovers

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Catherine Broussard, Edward W. Bush and Ann Gray

The best choice for shady areas where light is a limiting factor in turfgrass growth is a groundcover. Typical lawn grasses are physiologically incapable of surviving such locations. It is better to choose a groundcover adapted to shade than try to get grass to grow. In a deep shade environment no amount of fertilizing or watering can replace sunlight.

A groundcover is a reasonably low-growing, attractive, ideally evergreen plant used in place of grass, rocks, pebbles, organically derived mulching materials or earth in an area that might otherwise be devoid of vegetation. In the landscape, groundcovers can add visual interest by softening architectural features, adding foliage and flower color, height and textural patterns, and edging walks or ornamental beds. Continuity is provided in the landscapes by tying together mature plant specimens with new additions or bridging a garden’s formality with informal aspects.

Practically, groundcovers can be used to reduce erosion on steep or difficult slopes, and they function as living mulch under trees and shrubs. They also work to guide onlookers through the landscape.

Groundcovers do not require the intense maintenance that lawns require, so time is saved on mowing, raking, edging, weeding, watering, feeding, liming, and insect and disease control. Lawn maintenance chemicals are not required, so harmful runoff from rainfall or irrigation is reduced. Groundcovers moderate soil temperature and reduce water loss by reducing evaporation, allowing water percolation. These plants have greater tolerance to insects and disease than lawns.

Two of the most reliable and widely used groundcovers in Louisiana are liriope and mondograss (monkey grass). Collectively, these are also referred to as border grass. These groundcovers are known for their versatility in the landscape and thrive in many degrees of sun and shade.

Liriope and mondograss are originally native to Eastern Asia and were introduced to the West 200 years ago. They are generally known to perform best in moist fertile soils in partial shade but actually tolerate dry, poor and thin soils in sunny or shady sites. They are propagated primarily by division and infrequently by seed.

Though insects cause minimal problems, scale has been noticed to be a problem on some varieties. However, this can be controlled by pruning the foliage in the late fall or early winter. In the past few years, a crown rot disease has led to significant losses of various liriope and mondograss varieties in the landscape and nursery production settings. Several fungi and certain environmental and cultural conditions can cause leaf and crown rot of liriope. In some varieties leaf discoloration at the tips and red leaf spots associated with rust also are found at various times of the year.

Because of their versatility and reliability, liriope and mondograss have become as much of a Southern tradition in the landscape as azaleas, magnolias and crape myrtles. Liriope grows as a mass of varying shades of green or variegated leaves similar in appearance to grass and is used as a ground cover, a border, an interesting specimen in the landscape or even as a container plant.

Liriope flowers grow on stalks from the crown through the middle of the foliage. This is the striking feature of liriope. Depending on variety, the color can be white, lilac, pink or purple.

Mondograss is a mass of thin dark green leaves that resemble grass. The white flowers bloom in May but are inconspicuous on short stalks hidden within the leaves. Once established, mondograss multiplies rapidly, out-competing weeds and other vegetation.

Because of the numerous varieties of liriope and mondograss (dwarf, black, variegated), the various settings for which they can be used, and consumer preferences for varying foliage and flower characteristics, LSU AgCenter scientists conducted an experiment at Burden Center. The three-year study consisted of 19 varieties and two treatments, one with sun and the other with shade and was replicated six times.

Following is the list of the ten plants of the 19 studied. Big Blue is the only one that did better in the sun than the shade.

Best in the shade were mondograss, dwarf mondograss, Supergreen, aztecgrass, variegated mondograss, Royal Purple, Variegata, Webster, Christmas Tree and Samantha.

Best in the sun were dwarf mondograss, Supergreen, Variegata, Big Blue, mondograss, Densiflora, Royal Purple, Samantha, Silvery Midget and Webster.

Best overall were dwarf mondograss, Supergreen, mondograss, Variegata, Royal Purple, Webster, variegated mondograss, aztecgrass, Samantha and Big Blue.

Catherine Broussard, Graduate Student; Edward W. Bush, Associate Professor; and Ann Gray, Research Associate, Department of Horticulture, LSU AgCenter, Baton Rouge, La.

(This article was published in the spring 2005 issue of Louisiana Agriculture.)

5/17/2005 3:09:03 AM
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